Semi-automatic firearms, such as rifles and shotguns, are designed to fire a round of ammunition, such as a cartridge or shotshell, in response to each squeeze of the trigger of the firearm, and thereafter automatically load the next shell or cartridge from the firearm magazine into the chamber of the firearm. During firing, the primer of the round of ammunition ignites the propellant (powder) inside the round, producing an expanding column of high pressure gases within the chamber and barrel of the firearm. The force of this expanding gas propels the bullet/shot of the cartridge or shell down the barrel.
In semi-automatic rifles and shotguns, a portion of the expanding gases typically are directed through a duct or port that interconnects the barrel of the firearm to a piston assembly that generally houses an axially moveable piston. The portion of the explosive gases that are diverted from the barrel of the firearm act upon the piston so as to force the piston rearwardly to thus cause the rearward motion, or recoil of the bolt of the firearm. This rearward motion opens the chamber and ejects the empty shell or cartridge casing, and thereafter loads another shell or cartridge into the chamber, after which the bolt returns to a locked position for firing as the gases dissipate or are bled off.
Known gas actuating piston assemblies for semi-automatic firearms can suffer from numerous disadvantages, however, including the inability to regulate the gas energy being transmitted to the piston. For example, the pressure of the diverted gases is often unequally distributed against the gas piston, thereby causing uneven movement of the piston that can result in rapid deterioration and/or damage to the piston. Also, when lower power cartridges or shells are used, the pressure of the discharge gases sometimes is not sufficient to properly or fully actuate/drive the piston assembly, which can result in misfired or jammed shells or cartridges. Further, the inventor has discovered that there is a relationship between the magnitude of the pressure impulse delivered by the discharge gases and the distance from the chamber of the firearm to the gas piston.
It therefore can be seen that a need exists for firearm that addresses the foregoing and other related and unrelated problems in the art.